PIK3CA and neoplasm: Type 1 endometrial cancer is most commonly characterized by mutation of PTEN, a tumor suppressor; and also by mutations in v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (K-ras), β-catenin, phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) and phosphatidylinositol 3-kinase (PIK3).